A beam of plane polarised light falls normally on a polariser (cross sectional area `3 xx 10^(-4)m^(2)`) which rotates about the axis of the ray with an angular velocity of `31.4 rad//s`. Find the energy of light passing through polariser per revolution and the intensity of emergent beam, if flux of energy of the incident ray is `10^(-3) W`.
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Here, cross sectional area of the polariser, `A = 3 xx 10^(-4)m^(2)` Angular velocity of polariser, `omega = 3.14 rad//s`. Flux of energy of incident ray `=10^(-3)W` `:.` Intensity of incident light, `I_(0) = ("flux of energy")/("Area") = (10^(-3))/(3 xx 10^(-4) W//m^(2)` Intensity of emergrnt polarised light, `I = (I_(0))/(2) = (10^(-3))/(2 xx 3 xx 10^(-4)) = (5)/(3) W//m^(2)` Energy of the light passing through the polariser per revolution ,brgt `W = I xx A xx T = I xx A xx (2pi)/(omega)` `= (5)/(3) xx 3 xx 10^(-4) xx (2 xx 3.14)/(3.14) = 10^(-4) J`
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